Support Ruby 3.0 and up

[mvz]

• Drop support for Ruby 2.7
• Build with Rubies 3.0 through 3.3 in CI

[mvz]

WTF!?

irb(main):001> RUBY_VERSION
=> "3.3.0"
irb(main):002> name = "UncommunicativeMethodName"
=> "UncommunicativeMethodName"
irb(main):003> name.split(/ *(?=[A-Z][a-z])/)
=> ["UncommunicativeMethodName"]
irb(main):004> name = "UncommunicativeParameterName"
=> "UncommunicativeParameterName"
irb(main):005> name.split(/ *(?=[A-Z][a-z])/)
=> ["Uncommunicative", "Parameter", "Name"]

[mvz]

Seems related to this: https://bugs.ruby-lang.org/issues/20095

[mvz]

I'm going to open another PR first to fix support for Ruby 3.3. After that, we can decide about Ruby 2.7.